First, what is kaiseki? In short, it is a meal that host prepares by himself/herself for the guests to enjoy before proceeding to a tea drinking. When the Tea tradition just came to Japan, kaiseki that has been served before tea gatherings consisted of many kinds of different foods. Guests were having a huge party. To illustrate it you can read a following poem traditionally attributed to Soami (d.1525), which is found in the Choka Chanoyu Monogatari [Tea stories in Long-verse style]. Soami was a cultural advisor to the Muromachi shogun.
Now they get down to the meal.
Raw fish, chicken, and everything else.
They lift the lids with haste,
And grab with bare hands
The raw-smelling dishes,
These overindulgent, gluttonous people.
The beautifully laid out dishes
They turn upside-down and spill around.
They even crunch on the bones,
Mixing many things in their mouths,
Using their chopsticks in the wrong way.
Their chatter is mingled with songs,
They prattle about the most trivial subjects;
Their voices rise as they compete,
Each pretending to know everything.
They take no note of prearranged times.
Lifting up the large sake cups,
They force themselves to drink
Much more than they are capable of,
Till their behavior becomes undignified.
You can see that Tea gatherings were not always the way we know it now. Rikyu did his best to transform the Way of Tea into a spiritual practice, in a wabi style.
From an article " From kaiseki to kaiseki: The development of Formal Tea Cuisine":
"One winter morning Sen Doan (1546-1607) invited his father, Sen Rikyu (1522-1591), to attend a snow-viewing tea. When Rikyu arrived he glanced into the front garden and saw Doan, wearing a straw raincoat and a sedge hat. Doan had been gathering vegetables in a nearby field and was just returning home.
When the meal trays were carried into the tearoom and Rikyu - in pleasurable anticipation of banishing the early-morning cold - removed the lid from his soup bowl, he found that the bowl contained sea bass and some greens. However, sea bass was out of season, and therefore scarce and expensive. Rikyu had been wondering about Doan's plans for the meal ever since he had glimpsed him returning from the field, and the chilly mood created by the soup was very disappointing to him. He chided his son for his lack of sensibility, emphasized that the cuisine for tea in wabi-soan (simple and unpretentious "grass hut") was first and foremost a matter of doing one's best to convey the atmosphere of wabi, and certainly not of serving rare delicacies. For Rikyu the ideal kaiseki, or "tea cuisine", was a simple cuisine using ordinary ingredients; a "down-to-earth" kind of meal."
Kaiseki that our class has prepared once for a tea gathering; fried squid and pieces of avocado.